Optical remote sensing measurements of bromine and sulphur emissions: Investigating their potential as tracers of volcanic activity

The optical remote sensing of volcanic gas emissions has become an established field in recent decades. The total amount of gas emissions (quantified by measuring the SO2 emission rate) as well as the composition of gases, can help researchers to understand volcanic systems. This knowledge is needed to improve forecasts of volcanic eruptions. For this thesis, volcanic gas emissions were investigated with two different techniques on different time scales. First, high time-resolution (order of 1 s) 2D-SO2 column density images measured by an SO2 camera were used to quantify SO2 emission rates at Popocatépetl, Mexico, and Stromboli, Italy. The frequency of the flux was investigated with a wavelet analysis. It was verified that calibrating the SO2 camera with help of a DOAS system leads to more robust results than using calibration cells, especially for a volcanic plume containing ash or aerosols. Second, spectra from the scanning DOAS network NOVAC (with a time resolution of ≈ 5 – 15 minutes) were evaluated for BrO/SO2 ratios. It was shown that data from NOVAC actually has sufficient quality to evaluate spectra for BrO. An automatic evaluation algorithm was developed and used to create a four-year time series (2009 – 2013) of BrO/SO2 ratios at Nevado del Ruiz, Colombia. The BrO/SO2 ratio showed variations that are closely correlated to the level of volcanic activity indicating its usefulness as an additional volcanological parameter. Several possibilities for further improving data quality were investigated. This included temperature effects on the DOAS retrieval, the influence of radiative transfer and problems arising from reference spectra contaminated with SO2

Communication between process and structure : modelling and simulating message reference networks with COM/TE

Focusing on observable message signs and referencing structures, communication processes can be described and analysed as message reference networks which are characterized by dynamic pattern evolution. Computational simulation provides a way of obtaining insights into the factors driving such processes. Our paper describes a theoretical framework for communication-oriented modelling — the COM approach — that is centred around the notion of social visibility as a reputation mechanism. The approach contrasts with agent-based social networks on the one hand, and with bibliometric document networks on the other. In introducing our simulation environment COM/TE, typical properties of message reference networks are discussed in terms of a case study which deals with the impact of different media and styles of communication on emergent patterns of social visibility

BrO/SO2 molar ratios from scanning DOAS measurements in the NOVAC network

The molar ratio of BrO to SO2 is, like other halogen/sulfur ratios, a possible precursor for dynamic changes in the shallow part of a volcanic system. While the predictive significance of the BrO/SO2 ratio has not been well constrained yet, it has the major advantage that this ratio can be readily measured using the remote-sensing technique differential optical absorption spectroscopy (DOAS) in the UV. While BrO/SO2 ratios have been measured during several short-term field campaigns, this article presents an algorithm that can be used to obtain long-term time series of BrO/SO2 ratios from the scanning DOAS instruments of the Network for Observation of Volcanic and Atmospheric Change (NOVAC) or comparable networks. Parameters of the DOAS retrieval of both trace gases are given. The influence of co-adding spectra on the retrieval error and influences of radiative transfer will be investigated. Difficulties in the evaluation of spectroscopic data from monitoring instruments in volcanic environments and possible solutions are discussed. The new algorithm is demonstrated by evaluating data from the NOVAC scanning DOAS systems at Nevado del Ruiz, Colombia, encompassing almost 4 years of measurements between November 2009 and end of June 2013. This data set shows variations of the BrO/SO2 ratio several weeks prior to the eruption on 30 June 2012

Twisted Superconducting Semilocal Strings

A new class of twisted, current carrying, stationary, straight string solutions having finite energy per unit length is constructed numerically in an extended Abelian Higgs model with global SU(2) symmetry. The new solutions correspond to deformations of the embedded Abrikosov-Nielsen-Olesen (ANO) vortices by a twist -- a relative coordinate dependent phase between the two Higgs fields. The twist induces a global current flowing through the string, and the deformed solutions bifurcate with the ANO vortices in the limit of vanishing current. For each value of the winding number $n=1,2...$ (determining the magnetic flux through the plane orthogonal to the string) there are $n$ distinct, two-parametric families of solutions. One of the continuously varying parameters is the twist, or the corresponding current, the other one can be chosen to be the momentum of the string. For fixed values of the momentum and twist, the $n$ distinct solutions have different energies and can be viewed as a lowest energy ``fundamental'' string and its $n-1$ ``excitations'' characterized by different values of their ``polarization''. The latter is defined as the ratio of the angular momentum of the vortex and its momentum. In their rest frame the twisted vortices have lower energy than the embedded ANO vortices and could be of considerable importance in various physical systems (from condensed matter to cosmic strings).Comment: 39 pages, 20 figure

Remote sensing of volcanic CO2, HF, HCl, SO2, and BrO in the downwind plume of Mt. Etna

Remote sensing of the gaseous composition of non-eruptive, passively degassing volcanic plumes can be a tool to gain insight into volcano interior processes. Here, we report on a field study in September 2015 that demonstrates the feasibility of remotely measuring the volcanic enhancements of carbon dioxide (CO2), hydrogen fluoride (HF), hydrogen chloride (HCl), sulfur dioxide (SO2), and bromine monoxide (BrO) in the downwind plume of Mt. Etna using portable and rugged spectroscopic instrumentation. To this end, we operated the Fourier transform spectrometer EM27/SUN for the shortwave-infrared (SWIR) spectral range together with a co-mounted UV spectrometer on a mobile platform in direct-sun view at 5 to 10 km distance from the summit craters. The 3 days reported here cover several plume traverses and a sunrise measurement. For all days, intra-plume HF, HCl, SO2, and BrO vertical column densities (VCDs) were reliably measured exceeding 5 x 10(16), 2 x 10(17), 5 x 10(17), and 1 x 10(14) molec cm(2), with an estimated precision of 2.2 x 10(15), 1.3 x 10(16), 3.6 x 10(16), and 1.3 x 10(13) molec cm(2), respectively. Given that CO2, unlike the other measured gases, has a large and wellmixed atmospheric background, derivation of volcanic CO2 VCD enhancements (Delta CO2) required compensating for changes in altitude of the observing platform and for background concentration variability. The first challenge was met by simultaneously measuring the overhead oxygen (O-2) columns and assuming covariation of O-2 and CO2 with altitude. The atmospheric CO2 background was found by identifying background soundings via the coemitted volcanic gases. The inferred Delta CO2 occasionally exceeded 2 x 10(19) molec cm(-2) with an estimated precision of 3.7 x 10(18) molec cm(-2) given typical atmospheric background VCDs of 7 to 8 x 10(21) molec cm(-2). While the correlations of Delta CO2 with the other measured volcanic gases confirm the detection of volcanic CO2 enhancements, correlations were found of variable significance (R-2 ranging between 0.88 and 0.00). The intra-plume VCD ratios Delta CO2/SO2, SO2/HF, SO2/HCl, and SO2/BrO were in the range 7.1 to 35.4, 5.02 to 21.2, 1.54 to 3.43, and 2.9 x 10(3) to 12.5 x 10(3), respectively, showing pronounced day-to-day and intra-day variability

Projektmanagement im "Unmarked Space" : Forschungsprojekte im Spannungsfeld von Industrie und Wissenschaft

Wer kennt das nicht aus Projekten, die zwischen Wissenschaft und Wirtschaft stattfinden: Es erscheint der Eindruck, als ob zwei verschiedene Welten/Kulturen zusammentreffen. Dies spiegelt sich nicht nur in der Zielformulierung und in der Herangehensweise wider, sondern auch wie Projektmanagement gelebt wird. In der spm Fachgruppe "Projektmanagement in der Forschung" hat man sich etwas eingehender mit dieser Thematik befasst, eigene Erfahrungen diskutiert sowie die Ergebnisse aus einer kleinen, nicht repräsentativen Umfrage analysiert. Sind die Unterschiede wirklich so gross, wie sie wahrgenommen werden? Im vorliegenden Artikel finden Sie Antworten und Handlungsempfehlungen dazu

Variation of the BrO/SO2 molar ratio in the plume of Tungurahua volcano between 2007 and 2017 and its relationship to volcanic activity

International audienceRecent long-term observations of the bromine monoxide (BrO) to sulphur dioxide (SO2) molar ratio in volcanic plumes have suggested a link between changes in the BrO/SO2 ratio and the volcanic activity. Nevertheless, understanding of the mechanisms determining this link is still limited due to the lack of studies on volcanic bromine release from the melt into the atmosphere. We present the results of 10 years (2007–2017) of observations of the BrO/SO2 molar ratio in the volcanic plume of Tungurahua volcano, Ecuador. Following the nearly continuous eruptive activity from 1999 to 2008, Tungurahua showed alternating phases of eruptive activity separated by periods of quiescence between late 2008 and March 2016, after which degassing intensity decreased below detection. By comparing the BrO/SO2 molar ratios collected from 13 eruptive phases to volcanic activity, this study aims to broaden the global observational database investigating their link. For this purpose, we combine three different methods to retrieve the BrO/SO2 molar ratio to analyse variations over different timescales. We identify a cyclic pattern in BrO/SO2 molar ratios for 11 of the 13 eruptive phases. The phases are initialised by low BrO/SO2 molar ratios between 2 and 6 × 10−5 coinciding with vulcanian-type activity followed by a strong increase to ratios ranging between 4 and 17 × 10−5 when eruptive dynamism shifts to strombolian. For five phases, we additionally observe a progressive decrease to the initial values of 2 to 5 × 10−5 toward the end of the phase. This clear pattern indicates a connection between the BrO/SO2 molar ratio and eruptive dynamics. Based on our new data, we propose a conceptual model of the volcanic processes taking place at Tungurahua during the eruptive phases. Our data furthermore indicate that maximal BrO/SO2 molar ratios observed during each phase could be related to the input of volatile-rich magma into the active part of the volcanic system of Tungurahua. This study shows that long-term BrO/SO2 molar ratios can be used as a proxy for the volatile status as well as temporal evolution of the volcanic system

In-operation field-of-view retrieval (IFR) for satellite and ground-based DOAS-type instruments applying coincident high-resolution imager data

Knowledge of the field of view (FOV) of a remote sensing instrument is particularly important when interpreting their data and merging them with other spatially referenced data. Especially for instruments in space, information on the actual FOV, which may change during operation, may be difficult to obtain. Also, the FOV of ground-based devices may change during transportation to the field site, where appropriate equipment for the FOV determination may be unavailable.This paper presents an independent, simple and robust method to retrieve the FOV of an instrument during operation, i.e. the two-dimensional sensitivity distribution, sampled on a discrete grid. The method relies on correlated measurements featuring a significantly higher spatial resolution, e.g. by an imaging instrument accompanying a spectrometer. The method was applied to two satellite instruments, GOME-2 and OMI, and a ground-based differential optical absorption spectroscopy (DOAS) instrument integrated in an SO2 camera. For GOME-2, quadrangular FOVs could be retrieved, which almost perfectly match the provided FOV edges after applying a correction for spatial aliasing inherent to GOME-type instruments. More complex sensitivity distributions were found at certain scanner angles, which are probably caused by degradation of the moving parts within the instrument. For OMI, which does not feature any moving parts, retrieved sensitivity distributions were much smoother compared to GOME-2. A 2-D super-Gaussian with six parameters was found to be an appropriate model to describe the retrieved OMI FOV. The comparison with operationally provided FOV dimensions revealed small differences, which could be mostly explained by the limitations of our IFR implementation. For the ground-based DOAS instrument, the FOV retrieved using SO2-camera data was slightly smaller than the flat-disc distribution, which is assumed by the state-of-the-art correlation technique. Differences between both methods may be attributed to spatial inhomogeneities.In general, our results confirm the already deduced FOV distributions of OMI, GOME-2, and the ground-based DOAS. It is certainly applicable for degradation monitoring and verification exercises. For satellite instruments, the gained information is expected to increase the accuracy of combined products, where measurements of different instruments are integrated, e.g. mapping of high-resolution cloud information, incorporation of surface climatologies. For the SO2-camera community, the method presents a new and efficient tool to monitor the DOAS FOV in the field.Atmospheric Remote Sensin